[−][src]Trait async_std::io::BufRead

pub trait BufRead {
    fn read_until<'a>(
        &'a mut self, 
        byte: u8, 
        buf: &'a mut Vec<u8>
    ) -> ImplFuture<'a, Result<usize>>
    where
        Self: Unpin,
    { ... }

    fn read_line<'a>(
        &'a mut self, 
        buf: &'a mut String
    ) -> ImplFuture<'a, Result<usize>>
    where
        Self: Unpin,
    { ... }

    fn lines(self) -> Lines<Self>
    where
        Self: Unpin + Sized,
    { ... }
}

Allows reading from a buffered byte stream.

This trait is an async version of std::io::BufRead.

While it is currently not possible to implement this trait directly, it gets implemented automatically for all types that implement futures::io::AsyncBufRead.

Provided methods

fn read_until<'a>(
    &'a mut self,
    byte: u8,
    buf: &'a mut Vec<u8>
) -> ImplFuture<'a, Result<usize>> where
    Self: Unpin, 

Reads all bytes into buf until the delimiter byte or EOF is reached.

This function will read bytes from the underlying stream until the delimiter or EOF is found. Once found, all bytes up to, and including, the delimiter (if found) will be appended to buf.

If successful, this function will return the total number of bytes read.

Examples

use async_std::fs::File;
use async_std::io::BufReader;
use async_std::prelude::*;

let mut file = BufReader::new(File::open("a.txt").await?);

let mut buf = vec![0; 1024];
let n = file.read_until(b'\n', &mut buf).await?;

fn read_line<'a>(
    &'a mut self,
    buf: &'a mut String
) -> ImplFuture<'a, Result<usize>> where
    Self: Unpin, 

Reads all bytes and appends them into buf until a newline (the 0xA byte) is reached.

This function will read bytes from the underlying stream until the newline delimiter (the 0xA byte) or EOF is found. Once found, all bytes up to, and including, the delimiter (if found) will be appended to buf.

If successful, this function will return the total number of bytes read.

If this function returns Ok(0), the stream has reached EOF.

Errors

This function has the same error semantics as read_until and will also return an error if the read bytes are not valid UTF-8. If an I/O error is encountered then buf may contain some bytes already read in the event that all data read so far was valid UTF-8.

Examples

use async_std::fs::File;
use async_std::io::BufReader;
use async_std::prelude::*;

let mut file = BufReader::new(File::open("a.txt").await?);

let mut buf = String::new();
file.read_line(&mut buf).await?;

fn lines(self) -> Lines<Self> where
    Self: Unpin + Sized, 

Returns a stream over the lines of this byte stream.

The stream returned from this function will yield instances of io::Result<String>. Each string returned will not have a newline byte (the 0xA byte) or CRLF (0xD, 0xA bytes) at the end.

Examples

use async_std::fs::File;
use async_std::io::BufReader;
use async_std::prelude::*;

let file = File::open("a.txt").await?;
let mut lines = BufReader::new(file).lines();
let mut count = 0;

while let Some(line) = lines.next().await {
    line?;
    count += 1;
}
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Implementors

impl<T: AsyncBufRead + Unpin + ?Sized> BufRead for T[src]

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